One of the best simple yet very profound introductory texts on Theory of Elasticity. With detailed drawings relying on scalar 3D, consistent notation, is simple enough that an advanced undergraduate student can follow it while presents a complete discussion of constitutive relations, compatibility equations, and a several (non-trivial) explicit solutions to elasticity problems, like uniform torsion of triangular and square section bar, and some plate-shell developments too.
Excellent for those who wish to understand elasticity theory in order to put it into Finite Element analysis.